in reply to Re (using assertions): pattern matching a limited number of times
in thread pattern matching a limited number of times

How about a modified version of japhy's code. 
#!/usr/bin/perl -wT
use strict;

my $string  = 'abc ' x 10;
my $search  = 'ab';
my $replace = 'CD';

print "$string\n";

my $i = 0;
while ($string =~ /$search/gi) {
  substr($string, $-[0], $+[0]-$-[0], $replace);
  last if ++$i == 4;
  pos($string) = $-[0] + 1;
}

print "$string\n";

__END__
abc abc abc abc abc abc abc abc abc abc
CDc CDc CDc CDc abc abc abc abc abc abc

[download]
Update: Doh! I didn't see your very similar solution before I posted....

-Blake

Replies are listed 'Best First'.
Re: Re2: pattern matching a limited number of times
by bart (Canon) on Sep 14, 2002 at 10:14 UTC
    Doh! I didn't see your very similar solution before I posted....
    It is very similar, isn't it? And I hadn't seen yaphy's solution before I posted mine. Now, it left me wondering: is setting pos() necessary, or will Perl DWIM, and continue matching at the same point in the (original) string without help? That's what s///g does.

    Well, it turns out that it appears to be using an offset in the string to keep track of where it was. So it is necessary. 

    $_ = 'abxy' x 12;
for(my $i = 0; m/ab/g and $i++<5;) {
    substr($_, $-[0], $+[0]-$-[0]) = 'abXab';
}
print;

    [download]
    Result: abXabXabXabXabXabxyabxyabxyabxyabxyabxyabxyabxyabxyabxyabxyabxy

    Not good. 

    $_ = 'abxy' x 12;
for(my $i = 0; m/ab/g and $i++<5;) {
    substr($_, $-[0], $+[0]-$-[0]) = 'abXab';
    pos = $-[0]+5;
}
print;

    [download]
    Result: abXabxyabXabxyabXabxyabXabxyabXabxyabxyabxyabxyabxyabxyabxyabxy

    Good.

    p.s. I noticed this, which is also very awkward: 

    my $length = length(substr($_, 2, 2) = 'abXab');
print $length;

    [download]
    prints 2, not 5. What happened to the rule: the value of an assignment as an expression, is what you assign?
[reply]
[d/l]
[select]

      p.s. I noticed this, which is also very awkward:

      Aren't you simply being bitten by the same bug I reported here in thread which you commented on here?

      For reference, Perlbug assigned a ticket ID of [perl #16834].

      Well It's better than the Abottoire, but Yorkshire!
[reply]

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